This project is designed to investigate the relation of childhood nutrition to breast cancer risk factors, including age at menarche, adult height, weight, and fatness. Secondary purposes include tracking the development of overweight and obesity from birth through young adulthood, identification of possible "sensitive" or high-risk periods (with respect to obesity) in childhood and, more important, to identify the contribution of diet to the development of childhood and adult obesity. Detailed anthropometric data (height, weight, skinfold thickness, etc.) and demographic characteristics are currently available on a computer data base from the Fels Study and the Division of Human Biology of the Wright State School of Medicine. Up to 18 annual dietary and anthropometric assessments are available for "index" girls. Calorie, macro- and micronutrient data will be linked to an existing anthropometry computer file, including later adult height and weight. Nutrient composition will be calculated using the latest version of the USDA Handbook series. Nutrients will include the following: total energy (kilocalories); total fat, protein, and carbohydrate; saturated, polyunsaturated, and monounsaturated fat; cholesterol; dietary fiber; and vitamins and minerals (from food and supplementary sources).